Methods for adhesive height setting

ABSTRACT

Methods for adhering parts together using part gap spacers are provided herein. Part gap spacers are formed in a selected pattern and a selected height on a surface of at least one surface of two parts to be oppositely disposed. When disposed opposite each other, at least some of the part gap spacers contact the opposite surface, and establish a standoff distance that is generally uniform, and thereby creating voids. Adhesive is disposed in at least some of the voids to adhere the part surfaces to each other. Further methods comprise forming part gap spacers on multiple sides of a third part to be disposed intermediate two surfaces. The part gap spacers can be formed in a variety of shapes, including bumps, tapers, ribs, and flange edges.

RELATED APPLICATION

This divisional application claims priority from U.S. application Ser.No. 11/054,149, filed Feb. 8, 2005, and which is herein fullyincorporated by reference as if fully set forth and for all purposes.

BACKGROUND

1. Field of the Application

The present application is directed to devices for spacing parts in ahard disk drive assembly or a fluid dynamic bearing (FDB) motor.

2. Related Art

In the assembly of a fluid dynamic bearing motor, it is often desirableto use adhesives to bond or connect parts of the motor. However, thereare significant obstacles to using adhesives in a precision assemblythat bonds or connects parts. It is desirable to control bond linethickness for optimum bond strength. In addition, part toleranceaccumulation is larger when adhesives are used to connect the surfacesof two parts. In many applications, it is desirable for parts to befixed at substantially uniform distances during adhesive hardening. Inother applications, it is desirable for a bearing fluid to be disposedbetween adjacent parts. In other applications, it is desirable forelectric conductivity between parts to be controlled or restricted.

SUMMARY

In one aspect, the present application is directed to a device forspacing parts in a hard disk drive assembly or FDB motor. The deviceincludes two adjacent parts of a fluid dynamic bearing motor havingfacing surfaces. A plurality of gap spacers is disposed on one or moreof the facing surfaces of the two adjacent parts. The gap spacersprovide a substantially uniform distance between the two adjacent parts.

In one variation, each gap spacer is selected from the group consistingof a bump, a radial rib, a flange edge, and a taper. In anothervariation, the gap spacers are disposed on each facing surface of theadjacent parts.

In another aspect, adhesive or bearing fluid is disposed between the twoadjacent parts. In one variation, the adhesive can be an anaerobicadhesive. In another variation, the adhesive can be epoxy.

In another aspect, the present application is directed to a device forspacing parts in a hard disk drive assembly or FDB motor. First andsecond parts each have facing surfaces. An intermediate part havingfirst and second oppositely oriented surfaces is interposed between thefacing surfaces of the first and second parts. A plurality of gapspacers is disposed on at least one of the first surface of theintermediate part and the facing surface of the first part such that thefirst part is spaced a substantially uniform distance from theintermediate part. A plurality of gap spacers is disposed on at leastone of the second surface of the intermediate part and the facingsurface second part such that the second part is spaced a substantiallyuniform distance from the intermediate part.

In one variation, an adhesive is disposed between the first surface ofthe intermediate part and the facing surface of the first part. In afurther variation, the adhesive is also disposed between the secondsurface of the intermediate part and the facing surface of the secondpart. In a further variation, the adhesive is an anaerobic adhesive. Inanother variation, the adhesive is epoxy.

In another variation, a bearing fluid is disposed between the firstsurface of the intermediate part and the facing surface of the firstpart. In another variation, bearing fluid is disposed between the secondsurface of the intermediate part and the facing surface of the secondpart. Alternatively, an adhesive is disposed between a second surface ofthe intermediate part and the facing surface of the second part.

In a further variation, part gap spacers are electrically conductive,and provide for an electrical connection between adjacent parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a cross-sectional side view of two adhered parts offsetby a triad of spacer gap bumps;

FIG. 2 depicts a cross-sectional side view two adhered parts offset byan intermediate part with bumps disposed on each side;

FIG. 3A depicts a perspective view of a cup having a series of bumpsdisposed on the upper and lower side of the bottom surface;

FIG. 3B depicts a cross-sectional side view of the cup of FIG. 3A;

FIG. 3C depicts a top view of the cup of FIG. 3A;

FIG. 4 depicts a cross-sectional side view of a fluid dynamic bearingmotor incorporating the cup of FIG. 3;

FIG. 5A depicts the top view of a part having radially aligned ribs;

FIG. 5B depicts a side view of the part of FIG. 5A;

FIG. 6A depicts the top view of a flange;

FIG. 6B depicts a cross-sectional side view of the flange of FIG. 6A;

FIG. 7A depicts the top view of a tapered part;

FIG. 7B depicts a cross-sectional side view of the part of FIG. 7A;

FIG. 7C depicts a cross-sectional side view of the part of FIG. 7Aadhered to an adjacent part.

DETAILED DESCRIPTION

The present application is directed to part gap spacers disposed betweenparts in a fluid dynamic bearing motor. Part gap spacers are designed tooff-set adjacent parts such that part-to-part spacing has less variationdue to tolerance accumulation. Part gap spacers also allow for greatercontrol of bond line thickness of adhesives. When an adhesive isdisposed between the two parts, the parts are maintained at asubstantially uniform distance during hardening. Part gap spacers reduceor eliminate the need for fixturing while adhesive hardens or cures.Part gap spacers can be configured to provide a substantially uniformstand-off distance between parts in applications where a fluid, such asa bearing fluid, flows between the parts. Further, part gap spacers canalso control part-to-part conductivity. In certain embodiments, part gapspacers are used to attach a high precision part to a low precisionpart.

In one embodiment, FIG. 1 shows device 100 having two adjacent parts 102and 104. Three bumps 106 are disposed on the surface 103 of part 102.The bumps 106 are part gap spacers. The substantially evenly spacedbumps 106 have a substantially uniform height with respect to thesurfaces 103 and 105, corresponding to parts 102 and 104, respectively.The bumps thereby provided a substantially uniform stand-off distancebetween parts 102 and 104.

As will be apparent to those of skill in the art, bumps may be disposedon the surfaces of either or both adjacent parts. The bumps protrude asubstantially uniform distance from the surfaces of each part. Theoffset distance between the parts is thereby a substantially uniformdistance.

When adhesive 112 is disposed between the surfaces of the adjacentparts, the bumps 106 define a substantially uniform distance between theparts 102 and 104, as well as an adhesive bond line thickness. Asadhesive 112 hardens, the substantially uniform distance between parts102 and 104 is maintained. Any adhesive known in the art may be used,including, but not limited to epoxy, two-part epoxy, ultraviolet (UV)cured epoxy, heat cure epoxy, pressure sensitive adhesive (PSA), andanaerobic adhesive.

Those of skill in the art will recognize that in other embodiments, anynumber of bumps may be arranged in any orientation or pattern on thesurfaces. The bumps can be oriented at random, or in a specific pattern(e.g., a grid or ring). When the part gap spacers are bumps, a minimumof three bumps are necessary to provide a substantially uniform part gapdistance.

The bump can be designed to provide a specific distance setting betweenparts. For example, the bump can be optimized for a specific adhesiveaccording to the adhesive manufacturer's recommendations. Alternatively,one of ordinary skill in the art could optimize the distance bump heightby experimenting with different bump sizes to determine which gapdistance is optimal for a specific adhesive.

The bumps can be disposed on the surfaces of each part to optimize asubstantially uniform stand-off distance between parts for a specificadhesive. In an exemplary embodiment, the adhesive is an epoxy. Undercertain circumstances, the gap distance for setting is greater than orequal to about 50 microns, greater than or equal to about 60 microns,greater than or equal to about 70 microns, greater than or equal toabout 80 microns, greater than or equal to about 90 microns, or greaterthan or equal to about 100 microns. For example, under the same ordifferent circumstances, the gap distance for setting is less than orequal to about 150 microns, less than or equal to about 140 microns,less than or equal to about 130 microns, less than or equal to about 120microns, less than or equal to about 110 microns, or less than or equalto about 100 microns. In certain circumstances, the gap distance forsetting is about 100 microns. The bumps can be designed to define adistance between adjacent surfaces. It will be recognized that the gapdistance can be adjusted to optimize the stand-off distance for anyadhesive.

Those of skill in the art will also recognize that the bumps can bearranged at locations where adhesive is desired. The bumps create acapillary force that attracts adhesive. Adhesive thereby collects aroundthe bumps. The bumps can thus be placed to influence distribution ofadhesive along the bond line. Bond strength can be optimized to specificloading requirements of a specific application. For example a circularbond area under bending moment loading would benefit from bumps toensure adhesive coverage near the circle perimeter where stress ishighest. Adhesive is attracted to the bump by capillary action, and isthus distributed along the bond line. The effect can be cumulative whenmultiple bumps are placed along the bond line.

The bumps can be configured to provide a substantially uniform stand-offdistance between parts in applications where a fluid, such as a bearingfluid, flows between the parts. For example, tolerances between attachedparts in a hard disk drive assembly or FDB motor can be optimized forspecific bearing fluids. The stand-off distance may also be set suchthat bearing fluid is not restricted and that there is substantially nopressure drop between the entry and exit points of bearing fluid. Thestandoff distance can be optimized for a specific bearing fluid. Theoffset distance in this case is a function of the cross-sectional areaof the flow and rate at which the bearing fluid flows.

In certain embodiments, the bumps are conductive, thereby providing anelectrical connection between the adjacent parts. The conductivematerial can be any conductive material known in the art. Conductivematerials include, but are not limited to, any metal or conductiveplastic. An adhesive placed between the parts can be conductive ornon-conductive. Likewise, a liquid bearing fluid placed between partscan be conductive or non-conductive.

In other embodiments, the bumps are constructed from an insulatingmaterial, thereby preventing an electrical connection between theadjacent parts. The insulating material can be any insulating materialknown in the art. Insulating materials include, but are not limited to,any non-conductive plastic. In such embodiments, an adhesive placedbetween parts is generally non-conductive. Likewise, a liquid bearingfluid placed between parts is generally non-conductive.

The following describes several additional embodiments. Persons skilledin the art will understand that the same principles and variations setforth above apply to each of these other embodiments. Those of skill inthe art will recognize that the various embodiments can be used alone orin combination.

In another exemplary embodiment, FIG. 2 depicts device 200 havingintermediate part 206 interposed between first part 202 and second part204. A series of bumps 208 are disposed on opposite sides ofintermediate part 206. Bumps 208 are part gap spacers. The intermediatepart 206 sets tolerances on facing surfaces of first and second parts202 and 204.

Intermediate part 206 sets the axial height and adhesive bond linethickness with respect to the first and second parts 202 and 204. Thebumps 208 on a first side 210 of intermediate part 206 define asubstantially uniform off-set distance with a first part 202, and thebumps 208 on the second side 212 of intermediate part 206 define asubstantially uniform offset distance with respect to second part 204.Adhesive 214 can be placed between one or both of the first and secondparts 202 and 204 and the intermediate part 206. Further, onlyintermediate part 206 includes bumps 208. In the embodiment of FIG. 2,only the intermediate part includes part gap spacers.

Those of skill in the art will recognize that the bumps can beconfigured such that bearing fluid flows readily between theintermediate part and each surface of the first part and the secondpart. The stand-off distance may also be set such that bearing fluid isnot restricted and that there is substantially no pressure drop betweenthe entry and exit points of bearing fluid. The standoff distance can beoptimized for a specific bearing fluid, as well as other factors knownto those skilled in the art of FDB design.

Those of skill in the art will also recognize that bumps can be disposedon the intermediate part in any arrangement. For example, anintermediary part having two evenly spaced planes defining outwardlyfacing bumps on each side acts as a part gap spacer between the surfacesof the two adjacent parts and the intermediary part. Part gap spacerallows for reduced tolerance accumulation when using adhesive to bondthe parts. The bumps are configured to provide a substantially uniformstand-off distance between the adjacent parts. The stand-off distancecan be optimized for a variety of factors, including the distancedesired between the two attached parts and the highest strengththickness of the adhesive used between the attached parts.

In certain embodiments, the intermediate part is conductive, therebyproviding an electrical connection between the first and second parts.The conductive material can be any conductive material known in the art.The material can be, but is not limited to, any conductive metal orconductive plastic. An adhesive placed between a part and theintermediate part can be a conductive adhesive or a non-conductiveadhesive. Likewise, a liquid bearing fluid placed between a part and theintermediate part can be a conductive bearing fluid or a non-conductivebearing fluid. Alternatively, the intermediate part can be an insulator.

Those of skill in the art will recognize that in other embodiments, anynumber of bumps may be arranged in any orientation or pattern on thesurfaces. The bumps can be oriented at random, or in a specific pattern(e.g., a grid or ring). The optimal amount of contact area between thepart gap spacer and the contacted surface can vary, and can depend, forexample, on the adhesive or bearing fluid used.

In another exemplary embodiment, FIGS. 3A-C depict a cup 300 havingbumps 302 disposed on its top and bottom. With reference to FIG. 3A, cup300 has sides 304 and bottom 306. With reference to FIG. 3B, the bottom306 of cup 300 has six radially distributed bumps 302 disposed thereon.In the present embodiment, three bumps face up, and three bumps facedown in alternating fashion. With reference to FIG. 3C, the bottom 306of cup 300 has bumps arranged on both its upper and lower surfaces.

FIG. 4 shows an embodiment of an FDB motor 320 configured with a cup 300of FIG. 3 disposed between motor sleeve and a motor base. The bumpsdisposed on each side of the cup 300 provide a substantially uniformstand-off distance between cup 300 and both the motor base 312 and themotor sleeve 310. Adhesive is disposed between the motor base 312 andthe bottom 306 of cup 300, thereby adhering motor base 312 to the cup300 at a substantially uniform distance. The substantially uniformstandoff between the cup 300 and motor base 312 provides substantiallyuniform precision spacing. The substantially uniform standoff betweencup 300 and sleeve 310 provides precision spacing for the flow ofbearing fluid between sleeve 310 and cup 300.

While the preceding embodiments disclose bumps as part gap spacers,those of skill in the art will recognize that bumps are but one exampleof a part gap spacer. Other part gap spacers include, withoutlimitation, radial ribs, flange edges, and tapers. Persons skilled inthe art will understand that the same principles and variations setforth above apply to each of these other embodiments.

FIGS. 5A and 5B show another embodiment of the present application. Withreference to FIG. 5A, part 400 has a series of radial ribs 402 disposedon part surface 401. With reference to FIG. 5B, ribs 402 are part gapspacers. Specifically, the ribs have a substantially uniform height withrespect to the part surface 401. When device 400 is placed against anadjacent part (not shown), ribs 402 provide a substantially uniformstand-off distance between part surface 401 and the adjacent part.

As will be apparent to those of skill in the art, ribs may be disposedon the surfaces of either or both adjacent parts. In such embodiments,the ribs protrude a substantially uniform distance from the surfaces ofeach part. The offset distance between the parts is a substantiallyuniform distance. Although ribs 402 of the present embodiment aredisposed radially around part surface 401, in other embodiments ribs canbe disposed in any direction on a part surface. Any number of ribs maybe arranged in any orientation or pattern on the surfaces. The ribs canbe oriented at random, or in a specific pattern.

As discussed with respect to the embodiments of FIGS. 1-4, adhesive canbe disposed between part 400 and a contact surface of an adjacent part(not shown). Any adhesive known in the art can be used, and the ribs canbe configured to optimize gap distances. The ribs can be configured toprovide a substantially uniform stand-off distance between parts inapplications where a fluid, such as a bearing fluid, flows between theparts.

FIGS. 6A and 6B show another embodiment of the present application. Part500 has an edge 502 that is a part gap spacer. Specifically, edge 502has a substantially uniform height with respect to the surface 501. Whenpart 500 is placed against an adjacent part (not shown), edge 502provides a substantially uniform stand-off distance between surface 501and the adjacent part.

As discussed with respect to the embodiments of FIGS. 1-5, adhesive canbe disposed between surface 501 and a contact surface of an adjacentpart (not shown). Any adhesive known in the art can be used, and theflange edge can be configured to optimize gap distances. The flange edgecan be configured to provide a substantially uniform stand-off distancebetween parts in applications where a fluid, such as a bearing fluid,flows between the parts.

FIGS. 7A-C shows another embodiment of the present application. Withrespect to FIGS. 7A and 7B, tapered part 600 has tapers toward thecenter 601 of part 600. The outer diameter of the taper forms taper edge602 that is a part gap spacer. Specifically, the taper has asubstantially uniform height with respect to the center 601 of part 600.

With respect to FIG. 7C, when part 600 is placed against adjacent part604, the taper provides a substantially uniform stand-off distancebetween taper edge 602 and adjacent part 604. Adhesive 608 can bedisposed between tapered part 600 and a surface 606 of adjacent part604. Capillary forces pull the adhesive toward the outer diameter oftapered part 600 to where taper edge 602 is located. Center area 610 canaccommodate excess adhesive. As discussed with respect to theembodiments of FIGS. 1-4, any adhesive known in the art can be used, andthe taper can be configured to optimize gap distances.

As will be apparent to those of skill in the art, two adjacent parts maybe tapered. In such embodiments, the offset distance between the partsis a substantially uniform distance. Although the tapers of the presentembodiment are disposed at the edge of part 600, the tapered edge at anypoint on part surface 600.

It will be recognized that part gap spacers such as ribs, flange edges,and tapered parts can be disposed on an intermediate part that can bedisposed between adjoining parts in a manner similar to the embodimentsof FIGS. 1-4.

In certain embodiments, gap spacers disposed on the part surface orintermediate part surface may be designed with a specific shape. Forexample, the gap spacers may be designed such that the adhesive mustflow to a specific location between two surfaces. When an adhesive isapplied, it flows to the narrowest space between attached parts. Anarray of gap spacers can be shaped such that the adhesive flows to adesired location.

It will be recognized that gap spacers can be disposed on a partparallel to the axial direction as well as a part parallel to the radialdirection.

It will also be recognized that gap spacers can be designed according toany method known in the art. For example, in one embodiment the gapspacers can be stamped into one or more surfaces of the adjacent parts,or on one or more sides of the intermediate part. In other embodiments,gap spacers can be designed by precision molding. Generally speaking,any method of preparing parts can be used.

Although the foregoing has been described in some detail by way ofillustration and example for purposes of clarity of understanding, it isreadily apparent to those of ordinary skill in the art in light of theteachings of the present application that certain changes andmodifications may be made thereto without departing from the spirit andscope of the claims. Applicants have not abandoned or dedicated to thepublic any unclaimed subject matter.

1. A method for adhering surfaces of parts, comprising: forming aplurality of spacing elements on a surface of a first part to be adheredto a surface of a second part, the plurality of spacing elements formedin a selected pattern and having a selected height from the surface ofthe first part; disposing the surfaces opposite each other, at leastsome of the spacing elements contacting the surface of the second part,and defining a plurality of voids in conjunction with the surfaces ofthe first part and the second part; and disposing adhesive in at leastsome of the voids to adhere the surfaces to each other.
 2. The method ofclaim 1, further comprising selecting the spacing element pattern toprovide formation of spacing elements at points where higher loads areexpected.
 3. The method of claim 1, wherein the surface of the firstpart is radially shaped, and further comprising selecting a radialspacing element pattern for formation at an outer periphery of thesurface of the first part, for resisting bending loads.
 4. The method ofclaim 1, further comprising selecting the height of the spacing elementsbased on properties of the adhesive.
 5. The method of claim 1, furthercomprising selecting an amount of contact area between the spacingelements and the first surface of the second part.
 6. The method ofclaim 1, further comprising selecting the height of the spacing elementsto provide a stand-off distance less than or equal to about 150 microns.7. The method of claim 1, wherein the first part is cup shaped, and thesurface of the first part is a bottom surface of the cup shape, theplurality of spacing elements comprise bumps formed to protrudetherefrom.
 8. The method of claim 7, wherein the second part includes abase to a disc drive motor, and further comprising forming bumps toprotrude from a top surface of the cup shape, disposing a sleeveopposite the top surface of the cup shape, the bumps protruding from thetop surface providing a substantially uniform stand off distance betweenthe top surface of the cup shape and the sleeve, and disposing a bearingfluid a void established thereby.
 9. A method for constructing a devicefrom parts, comprising: providing a first part having a surface;providing a second part having a surface; determining a desired standoffdistance between the surfaces of the first part and the second part;providing a third part between the respective surfaces of the first partand the second part, the third part having a regular undulating shapecomprising a plurality of gap spacing formations, and causing asubstantially uniform standoff distance about equal to the desiredstandoff distance, with voids defined by the formations and respectivesurfaces of one or more of the first part and the second part; anddisposing either lubricating liquid or adhesive in at least some of thevoids.
 10. The method of claim 9, wherein the surface of the first partis machined to a first degree of precision and the surface of the secondpart is machined less precisely than the surface of the first part. 11.The method of claim 9, wherein the third part has a mid-section aboutwhich the gap spacing formations undulate such that alternating gapspacing formations are nearer the surface of the first part than thesurface of the second part.
 12. The method of claim 11, wherein thealternating gap formations define voids between the third part and thesurface of the second part.
 13. The method of claim 9, wherein the thirdpart has a mid-section about which the gap spacing formations undulatesuch that first alternating gap spacing formations are nearer thesurface of the first part than the surface of the second part, andsecond alternating gap spacing formations are nearer the surface of thesecond part than the surface of the first part.
 14. The method of claim13, wherein the first alternating gap spacing formations define voidsbetween the third part and the surface of the second part, and thesecond alternating gap spacing formations define voids between the thirdpart and the surface of the first part.
 15. The method of claim 9,wherein the determined desired standoff distance is less than about 150microns.
 16. The method of claim 9, further comprising selecting a shapefor the gap spacing formations from a set of shapes comprising bumps,ribs, flange edges, and tapers.
 17. The method of claim 9, furthercomprising stamping or molding the gap spacing formations in the thirdpart.
 18. The method of claim 9, wherein the step of disposingcomprising disposing adhesive in voids defined between the third partand the surface of the second part, and lubricating liquid in voidsdefined between the third part and the surface of the first part. 19.The method of claim 9, wherein the first part includes a base to a discdrive motor, the second part comprises a sleeve to the disc drive motor,the third part comprises a cup adapted for holding the sleeve, andfurther comprising forming the gap spacing formations on both a topsurface and a bottom surface of a bottom of the cup, adhering the cup tothe base, disposing the sleeve in the cup, adhering the base to the cupby disposing adhesive in voids established between the bottom surface ofthe cup and the base, and disposing bearing fluid in voids establishedbetween the top surface of the cup and the sleeve.
 20. A method ofadhering parts, comprising: defining a conical void in a surface of afirst part with an inwardly directed conical surface portion; disposingthe first part opposite a surface of a second part to form a capillarydefined by the interface between the surface of the first part and thesurface of the second part; and disposing adhesive initially proximatean edge of the conical surface portion and allowing some of the adhesiveto be drawn between the surface of the first part and the surface of thesecond part, while allowing excess adhesive to remain in the conicalvoid.